The TS crossings of the Voyager 1 (V1) and Voyager 2 (V2) missions in 2004 (\(\sim \) 94 AU; [1]}, [2]}) and 2007 (\(\sim \) 84 AU; [3]}, [4]}), respectively, led to the discovery of the reservoir of ions and electrons that constitute the IHS, where the particle pressure exceeds substantially the magnetic field pressure (\(\beta \) =P\(_{\mathrm {particle}}\) /P\(_{MAG}>>\) 1; [5]}, [6]}, [7]}). The IHS extends out to the HP, which serves as the interface between the SW plasma and the VLISM, that was measured in-situ by V1 in 2012 (\(\sim \) 122 AU; [8]}, [9]}, [10]}, [11]}) and by V2 in 2019 (\(\sim \) 119 AU; [12]}, [13]}, [14]}, [15]}, [16]}, revealing the dynamic nature of the boundary, that involves an increase in Galactic Cosmic Rays (GCR), magnetic field and temperature, a simultaneous decrease in suprathermal particles, invading of interstellar flux tubes into the IHS, pointing to the possibility of flux tube interchange instability at the boundary [10]}, [18]} and an outflow of suprathermal ions upstream at the HP out to \(\sim \) 28 AU, originating from inside the IHS [19]}. The activity upstream at the HP is summarized in [20]}, whereas a summary of the effects of the solar activity to the particle dynamics in interplanetary space, the IHS and the OHS is presented in [21]}.
